I did some testing to see how that function is working, and it didn't give me any error message when I tried it on my end. I definitely want to dig in a bit deeper and see what could've happened on your end.

What was the error message you received? Also, can you let me know the name of the campaign you noticed this in?

Thanks for providing the additional info. We tested this and couldn’t replicate this behavior. It likely was a one-time issue that you should not experience moving forward. But please do let us know if it persists!

Hi! This just happened again. The error message I get says "Hm. Something didn't quite work." I was sending to a group called Post Visit Her Paris 2017.12.15-24 and excluding a segment of people who already received the Post Visit email. After I sent the email, I tried to add these people to a group called "Received HP Post Visit Survey" when I received the error message. Is it because I'm excluding a segment?

Hmm, I'm sorry to hear you are still experiencing this issue. I am still unable to replicate this behavior on my side, but since this is an issue that continues to happen to you I'd like to look more into this. To do this it will be better for us to move this conversation over to our email system instead of it living here in Community. Can I get a good email where we can contact you?